Modern gasoline and diesel engines are more efficient and less polluting than similar engines of even a few years ago. However, due to the increased total number of vehicles in use, levels of air pollution continue to rise even in light of more efficient and clean running vehicles. Therefore, there has been increasing pressure to develop vehicles which have lower emissions, and thus are less polluting than conventional automotive technology permits. This has spurred development of alternate fuel technologies such as electric cars and vans, natural gas and propane fuelled vehicles, hydrogen cell vehicles and the like. While a number of these technologies are promising, some are still a long way from commercial implementation, and others appear to have reached the limit of present design capabilities without yielding a consumer acceptable product. Therefore, attention has refocused on conventional gas and diesel burning engines, and ways to render them more pollution free and efficient.
It is well known that the addition of hydrogen and oxygen gases as fuel increases the efficiency of an internal combustion engine and reduces pollution considerably. Both advantages appear to be the byproduct of faster flame speed that is as much as nine times that of gasoline, resulting in more complete combustion of the fuel in the combustion chamber. The amount of soot (semi-burnt hydrocarbons), nitrous oxide, carbon monoxide, and other pollutants is accordingly reduced, while output energy increases, for a greater fuel efficiency and horsepower.
One way to adopt hydrogen and oxygen as a fuel additive is to store the gases in tanks installed on a vehicle, with hoses connecting the tanks to the engine. However, tank storage of these volatile gases presents a persistent safety hazard, since there is always a risk of gas leak and explosion. It also requires regular trips to a service station for replenishment, which is inconvenient. Further, the prevailing service station network would need to be retrofitted at great cost to supply these gases, which would also require widespread coordination of standards that could unduly delay acceptance of the technology. As a result of these problems with tank storage, various attempts have been made to develop systems in which the gases could be generated on board the vehicle itself, using well-known technologies such as electrolysis, for use by the engine as needed.
An example of such a system is taught in U.S. Pat. No. 3,939,806 to Bradley. This system is quite complicated however since it includes a mechanism to generate DC current to power the electrolysis cell. This requires a working fluid such as water or freon and accompanying circulation system, a turbine and DC generator, a hydrogen carburetor and hydrogen storage tank, and several pumps to move the working fluid, water, and hydrogen. Implementing such a complicated system would be costly, require extensive effort to integrate with existing engines, and likely involve significant maintenance due to the many additional components. Further, Bradley does not even address the risk of an explosion, particularly from the hydrogen tank, or provide any means to keep the system running in cold weather, when the water that supplies the electrolysis cell would be frozen.
U.S. Pat. No. 5,231,954 to Stowe attempts to provide a simpler electrolysis system for generating hydrogen and oxygen gases on board a vehicle. The device is a single electrolysis chamber or cell that receives power directly from the vehicle battery, and has a gas-out line that connects with the positive crankcase ventilation (PCV) system of the engine. When the engine is running a vacuum is created in the PCV line which is used to draw the gases out of the cell and into the engine. There is also an air intake adjustment valve that is always open to the atmosphere. This valve is adjusted to mix air with the generated gases so as to meet emission control regulations. The operator adds electrolyte concentrate to water in the cell until a reading of 1.5–3.0 amperes is obtained. Thereafter, water is to be added manually to the cell about every 1000 miles. The cell has a friction-fit cap that secures tightly when exposed to the PCV line vacuum, and that loosens when the engine and associated vacuum is turned off. The loose cap is intended to pop off to provide relief from high pressure build-up in the cell when the engine is turned off.
Since the Stowe device receives power directly from the battery, the current level is set by adjusting the electrolyte concentration. The result is a high resistance, low current cell that generates excessive heat, which is problematic. The heat problem is exacerbated by the plastic walls used in the preferred embodiment, since plastic does not conduct heat well, and by the fact that no cooling mechanism is taught.
Further, while the device proposed aims to be simple to install and use, pre-mixing and pre-charging of the electrolyte is awkward, particularly for consumer use. Another complicating feature is that the air intake valve requires adjustment by emission control mechanics. Further, since this valve is always open to the atmosphere, it will likely draw dirty air into the cell. Stowe also teaches that this valve has a dual purpose in that it acts as a safety release valve if cell pressure rises. However it is not clear how an opening sized to meet emission requirements (likely a small opening) will also function effectively in a totally different context as a safety release. Therefore the Stowe device may lack sufficient safety release features to reduce the risk of explosion when there is a rise in pressure.
Yet another issue is that the PCV vacuum line required to operate the device is available with gasoline, but not diesel, internal combustion engines. Further, water replenishment is estimated at about every 1000 miles of driving. While this may be adequate for consumer use, it would require inconveniently frequent replenishment by commercial vehicle drivers who may drive that distance every few days. Therefore, the Stowe device would not be suitable for use by most commercial vehicles, particulary the large diesel trucks which produce a high proportion of pollution.
Another electrolysis device is shown in U.S. Pat. No. 4,271,793 to Valdespino. This patent teaches that the battery associated with most vehicle engines does not provide enough current to produce meaningful amounts of hydrogen and oxygen gases, and accordingly requires that a larger or second alternator be installed. However, this arrangement increases the amount of heat generated, which in turn requires installation of a separate water jacket supplied by the vehicle cooling system. These additional components add cost and complicate integration of the device with conventional engines.
The high level of generated heat presents a risk of boil-off of the electrolyte. To deal with this issue Valdespino places a valve in the output gas line to maintain a high cell internal pressure. The preferred pressure range is 50–150 psi, typically 100 psi. However, maintaining such high internal pressure generally increases the risk of an explosion and makes routine re-fill of the electrolyte a more complicated and risky procedure. It also compels the cell walls to be thicker than otherwise, adding to the weight of the cell. The gas output from the cell passes through an accumulator and from there is delivered to the intake manifold of the engine under a vacuum.
Unless these and other practical problems associated with this technology are resolved, the improved efficiency and reduced pollution benefits possible from using hydrogen and oxygen as a fuel additive will fail to be realized.